1. Field of the Invention
The present invention relates to an apparatus for supplying power to a package which consists of printed wiring boards and can be inserted to and withdrawn from a shelf and, more particularly, to an apparatus for supplying power to a plurality of packages which compose a high-density mounted communication system and require the supply of high capacity current.
2. Description of the Related Art
In recent years, the high-density of the communication system in a shelf configuration has been increasing the power consumption of each package which is a component of the system, and therefore, it is necessary to reliably supply high capacity current to the package.
In the conventional communication system having a plurality of packages which consume high power, connecting part which connects each package to the shelf and is disposed on a back wiring board, is composed of many pins and a large number of these pins are used for supplying power. For example, as shown in FIG. 9, which is a plan view of the connecting part, of 52 pins, a pin group 101 and a pin group 102, each group consisting of 20 pins, are used for supplying power for power supply plus side and minus side, respectively, and a pin group 103 consisting of other 12 points are used for the signal. Therefore, using many pins for supplying power enables high capacity current to be supplied to the package.
Such pin groups 101 and 102 for supplying power are disposed for each package, and in order to supply power from the shelf side to the pin group, a pattern on the power supply plus side for connecting the pin group on the power supply plus side is formed on the back wiring board on which the pin group is disposed, and a pattern on the power supply minus side for connecting the pin group on the power supply minus side is formed similarly, so that power is supplied from the shelf side to the pattern.
One method for supplying power from the shelf side to the pattern is to supply power by using a power supply connector for the pattern as shown in FIG. 10. The power supply connector 104 has the same shape as that of a signal connecting connector (not shown) and one connector 104 is provided for each shelf. Whereas the signal connecting connector is provided for each package to connect the signal line of the circuit in the package to the package circuit of another shelf via the signal pin 103 of the aforementioned connecting part. The power supply connector 104 connects the plus power supply from the shelf side to the pin group 101 for supplying power, and the minus power supply to the pin group 102 for supplying power. This connector 104 does not connect a signal line and is dedicated to power supply. Therefore, a package cannot be connected to the package side of the connecting part to which the power supply connector 104 is connected. In FIG. 9, reference numerals 105 and 106 denote patterns on the power supply plus and minus sides disposed on the back wiring board 107, respectively.
Another method for supplying power from the shelf side to the pattern is to supply power by fixing a power supply terminal to each pattern as shown in FIG. 11. In FIG. 11, the same reference numerals are applied to the elements common to FIG. 10, and the description is omitted. With the method to shown in FIG. 11, the power supply terminals 108 and 109 are fixed with screws to the patterns 105 and 106, respectively, so that power is supplied from the shelf side to the patterns 105 and 106.
In the conventional apparatus, however, of many pins composing the connecting part, a large number of pins must be used for power supply, so that there is a problem that the number of pins which can be used for the signal is decreased, despite the fact that it is naturally desirable to increase the number of pins using for the signal with the high-density of the system.
Further, the power is supplied to each package from the connector 104 or the terminal 108, 109 through a passage reaching the pin group for each package via the patterns 105 and 106 on the power supply plus and minus sides disposed on the back wiring board 107. However, since the increase in size of the patterns 105 and 106 is usually limited, the allowable amount of current of the patterns 105 and 106 is restricted, and a significant voltage drop occurs.
Further, as described above, a package cannot be connected to the package side of the connecting part to which the power supply connector 104 is connected, so that a wasteful space arises.